A new strain of norovirus is causing hundreds of outbreaks in the U.S. Norovirus is commonly called the stomach flu, though it’s not really the flu at all and is actually the #1 cause of food poisoning.

Dr. Jan Vinje with the Centers for Disease Control says that’s because it takes just a few particles to make someone sick and they’re harder to kill. In fact, the CDC says hand sanitizer alone will not cut it.

(Dr. Vinje) “Washing with soap and water, that’s what we recommend. As an add-on, then sanitizer can be used.”